Fluoxetine and norfluoxetine analysis by direct injection of human plasma in a column switching liquid chromatographic system

A column switching LC method is presented for the analysis of fluoxetine (FLU) and norfluoxetine (NFLU) by direct injection of human plasma using a lab-made restricted access media (RAM) column. A RAM-BSA-octadecyl silica (C-18) column (40 min x 4.6 mm, 10 mu m) is evaluated in both backflush and foreflush elution modes and coupled with a C-18 lab-made (50 mm x 4.6 mm, 3 pm) analytical column in order to perform online sample preparation. Direct injection of 100 mu L, of plasma samples is possible with the developed approach. In addition, reduction of sample handling is obtained when compared with traditional liquid-liquid extraction (LLE) and SPE. The total analysis time is around 20 min. A LOQ of 15 ng/mL is achieved in a concentration range of 15-500 ng/mL, allowing the therapeutic drug monitoring of clinical samples. The precision values achieved are lower than 15% for all the evaluated points with adequate recovery and accuracy. Furthermore, no matrix interferences are found in the analysis and the proposed method shows to be an adequate alternative for analysis of FLU in plasma.

High-performance liquid chromatographic separation and identification of polyphenolic compounds from the infusion of Davilla elliptica St. Hill

The isolation of polyphenolic compounds from an infusion of the Brazilian plant Davilla elliptica (Dilleniaceae), used as tea by virtue of its digestive properties, is described. An improved preparative HPLC method was used in order to isolate pure polyphenols from the complex mixture. Liquid-liquid extraction and solid-phase extraction were employed to minimise the interference of polymeric compounds and to provide an enriched fraction of the compounds of interest. The identification of the isolated compounds was performed using analytical HPLC as well as direct injection electrospray ionisation ion trap tandem mass spectrometry (ESI-IT-MS/MS). The high flavonoid content suggests that D. elliptica may be a promising source of compounds to produce natural phytomedicines. Copyright (C) 2007 John Wiley & Sons, Ltd.

Determination of aldicarb, aldicarb sulfoxide and aldicarb sulfone in some fruits and vegetables using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An analytical method for the determination of aldicarb, and its two major metabolites, aldicarb sulfoxide and aldicarb sulfone in fruits and vegetables is described. Briefly the method consisted of the use of a methanolic extraction, liquid-liquid extraction followed by solid-phase extraction clean-up. Afterwards, the final extract is analyzed by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). The specific fragment ion corresponding to [M-74](+) and the protonated molecular [M+K](+) ion were used for the unequivocal determination of aldicarb and its two major metabolites. The analytical performance of the proposed method and the results achieved were compared with those obtained using the common analytical method involving LC with post-column fluorescence detection (FL). The limits of detection varied between 0.2 and 1.3 ng but under LC-FL were slightly lower than when using LC-APCI-MS. However both methods permitted one to achieve the desired sensitivity for analyzing aldicarb and its metabolites in vegetables. The method developed in this work was applied to the trace determination of aldicarb and its metabolites in crop and orange extracts. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Determination of the geometrical diarylpropenamine isomers in feces by high-performance liquid chromatography

Diarylpropenamine derivatives are a class of compounds which have been evaluated as potential drug candidates. Here a specific and reproducible HPLC method for the determination of cis- and trans-isomers of the unsubstituted derivative, 3-(4'-bromo-[1,1'-biphenyl]-4-yl)-3-(4-X-phenyl-N,N-dimethyl-2-propen-1-amine (I, where X=H) in feces is described. The analyte I and internal standard, nitro derivative (II, where X=NO2), were isolated from the basified biological matrix using a liquid-liquid extraction with ethyl acetate followed by a solid-phase procedure performed on a silica cartridge. The organic phase was evaporated to dryness, the residue was reconstituted in mobile phase and injected into the HPLC system. The analytes were eluted with ethyl acetate-hexane-triethylamine (59:40:1) in HPLC column (silica) and detected by UV spectrophotometry at 272 nm. Linearity, precision and accuracy data for feces standards after extraction were acceptable. The method has been applied to analyses of feces samples from rats dosed with I, in which it could be anticipated that fecal excretion is quantitatively the major route for I elimination. Copyright (C) 1999 Elsevier Science B.V.

Assessing melatonin and its oxidative metabolites amounts in biological fluid and culture medium by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Analysis of ibuprofen enantiomers in rat plasma by liquid chromatography with tandem mass spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hydroxocobalamin quantification in human plasma by high-performance liquid chromatography coupled with electrospray tandem mass spectrometry in a pharmacokinetic study

A rapid, sensitive and specific method for quantifying hydroxocobalamin in human plasma using paracetamol as the internal standard (IS) is described. The analyte and the IS were extracted from plasma by liquid-liquid extraction using an organic solvent (ethanol 100%; -20°C). The extracts were analyzed by high performance liquid chromatography coupled with electrospray tandem mass spectrometry (HPLC-MS-MS). Chromatography was performed on Prevail C8 3 μm, analytical column (2.1×100 mm i.d.). The method had a chromatographic run time of 3.4 min and a linear calibration curve over the range 5-400 ng.mL-1 (r>0.9983). The limit of quantification was 5 ng.mL-1. The method was also validated without the use of the internal standard. The precision in the intra-batch validation with IS was 9.6%, 8.9%, 1.0% and 2.8% whereas without IS was 9.2%, 8.2%, 1.8% and 1.5% for 5, 15, 80 and 320 ng/mL, respectively. The accuracy in intra-batch validation with IS was 108.9%, 99.9%, 98.9% and 99.0% whereas without IS was 101.1%, 99.3%, 97.5% and 92.5% for 5, 15, 80 and 320 ng/mL, respectively. The precision in the inter-batch validation with IS was 9.4%, 6.9%, 4.6% and 5.5% whereas without IS was 10.9%, 6.4%, 5.0% and 6.2% for 5, 15, 80 and 320 ng/mL, respectively. The accuracy in inter-batch validation with IS was 101.9%, 104.1%, 103.2% and 99.7% whereas without IS was 94.4%, 101.2%, 101.6% and 96.0% for 5, 15, 80 and 320 ng/mL, respectively. This HPLC-MS-MS procedure was used to assess the pharmacokinetics of Hydroxo cobalamin following intramuscular injection 5000 μg in healthy volunteers of both sexes (10 males and 10 females). The volunteers had the following clinical characteristics (according to gender and expressed as mean ± SD [range]): males: age: 32.40 ± 8.00 y [23.00-46.00], height: 1.73 ± 0.07 m [1.62-1.85], body weight: 72.48 ± 10.22 Kg [60.20- 88.00]; females: age: 28.60 ± 9.54 y [18.00-44.00], height: 1.60 ± 0.05 m [1.54-1.70], body weight: 58.64 ± 6.09 Kg [51.70- 66.70]. The following pharmacokinetic parameters were obtained from the hydroxocobalamin plasma concentration vs. time curves: AUClast, T1/2, Tmax, Vd, Cl, Cmax and Clast. The pharmacokinetic parameters were 120 (± 25) ng/mL for Cmax, 2044 (± 641) ng.h/mL for AUClast, 8 (± 3.2) ng.mL-1 for Clast, 38 (± 15.8) hr for T1/2 and 2.5 (range 1-6) hr for Tmax. Female volunteers presented significant (p=0.0136) lower AUC (1706 ± 704) ng.h/mL) and larger (p=0.0205) clearance (2.91 ± 1.41 L/hr), as compared to male 2383 ± 343 ng.h/mL and 1.76 ± 0.23 L/hr, respectively. These pharmacokinetic differences could explain the higher prevalence of vitamin B12 deficiency in female patients. The method described validated well without the use of the internal standard and this approach should be investigated in other HPLC-MS-MS methods.

Microextraction techniques coupled to liquid chromatography with mass spectrometry for the determination of organic micropollutants in environmental water samples

[EN]Until recently, sample preparation was carried out using traditional techniques, such as liquid–liquid extraction (LLE), that use large volumes of organic solvents. Solid-phase extraction (SPE) uses much less solvent than LLE, although the volume can still be significant. These preparation methods are expensive, time-consuming and environmentally unfriendly. Recently, a great effort has been made to develop new analytical methodologies able to perform direct analyses using miniaturised equipment, thereby achieving high enrichment factors, minimising solvent consumption and reducing waste. These microextraction techniques improve the performance during sample preparation, particularly in complex water environmental samples, such as wastewaters, surface and ground waters, tap waters, sea and river waters. Liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) and time-of-flight mass spectrometric (TOF/MS) techniques can be used when analysing a broad range of organic micropollutants. Before separating and detecting these compounds in environmental samples, the target analytes must be extracted and pre-concentrated to make them detectable. In this work, we review the most recent applications of microextraction preparation techniques in different water environmental matrices to determine organic micropollutants: solid-phase microextraction SPME, in-tube solid-phase microextraction (IT-SPME), stir bar sorptive extraction (SBSE) and liquid-phase microextraction (LPME). Several groups of compounds are considered organic micropollutants because these are being released continuously into the environment. Many of these compounds are considered emerging contaminants. These analytes are generally compounds that are not covered by the existing regulations and are now detected more frequently in different environmental compartments. Pharmaceuticals, surfactants, personal care products and other chemicals are considered micropollutants. These compounds must be monitored because, although they are detected in low concentrations, they might be harmful toward ecosystems.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the quantitation of synthetic cannabinoids of the aminoalkylindole type and methanandamide in serum and its application to forensic samples

After the discovery of synthetic cannabimimetic substances in 'Spice'-like herbal mixtures marketed as 'incense' or 'plant fertilizer' the active compounds have been declared as controlled substances in several European countries. As expected, a monitoring of new herbal mixtures which continue to appear on the market revealed that shortly after control measures have been taken by legal authorities, other compounds were added to existing mixtures and to new products. Several compounds of the aminoalkylindole type have been detected so far in herbal mixtures but still their consumption cannot be detected by commonly used drug-screening procedures, encouraging drug users to substitute cannabis with those products. There is a increasing demand on the part of police authorities, hospitals and psychiatrists for detection and quantification of synthetic cannabinoids in biological samples originating from psychiatric inpatients, emergency units or assessment of fitness to drive. Therefore, a liquid chromatography-tandem mass spectrometry method after liquid-liquid extraction for the quantitation of JWH-015, JWH-018, JWH-073, JWH-081, JWH 200, JWH-250, WIN 55,212-2 and methanandamide and the detection of JWH-019 and JWH-020 in human serum has been developed and fully validated according to guidelines for forensic toxicological analyses. The method was successfully applied to 101 serum samples from 80 subjects provided by hospitals, detoxification and therapy centers, forensic psychiatric centers and police authorities. Fifty-seven samples or 56.4% were found positive for at least one aminoalkylindole. JWH-019, JWH-020, JWH-200, WIN 55,212-2 and methanandamide were not detected in any of the analyzed samples.

Measurement and stability of FTY720 in human whole blood by high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry

We report here a validated method for the quantification of a new immunosuppressant drug FTY720, using HPLC-tandem mass spectrometry. Whole blood samples (500 mu l) were subjected to liquid-liquid extraction, in the presence of an internal standard (Y-32919). Mass spectrometric detection was by selected reaction monitoring with an atmospheric pressure chemical ionization source in positive ionization mode (FTY720: m/z 308.3 -> 255.3). The assay was linear from 0.2 to 25 mu g/l (r(2) > 0.997, n = 5). The inter- and intra-day analytical recovery and imprecision for quality control samples (0.5, 7 and 15 mu g/l) were 95.8-103.2 and < 5.5%, respectively. At the lower limit of quantification (0.2 mu g/l) the interand intra-day analytical recovery was 99.0-102.8% with imprecision of < 7.6% (n = 5). The assay had a mean relative recovery of 100.5 +/- 5.8% (n = 15). Extracted samples were stable for 16 h. IFTY720 quality control samples were stable at room temperature for 16 h at 4 degrees C for at least 8 days and when taken through at least three freeze-thaw cycles. In conclusion, the method described displays analytical performance characteristics that are suitable for pharmacokinetic studies in humans. (c) 2006 Elsevier B.V. All rights reserved.

Parameters Affecting the Extraction of Polycyclic Aromatic Hydrocarbons with Pressurised Hot Water

Pressurised hot water extraction (PHWE) exploits the unique temperature-dependent solvent properties of water minimising the use of harmful organic solvents. Water is environmentally friendly, cheap and easily available extraction medium. The effects of temperature, pressure and extraction time in PHWE have often been studied, but here the emphasis was on other parameters important for the extraction, most notably the dimensions of the extraction vessel and the stability and solubility of the analytes to be extracted. Non-linear data analysis and self-organising maps were employed in the data analysis to obtain correlations between the parameters studied, recoveries and relative errors. First, pressurised hot water extraction (PHWE) was combined on-line with liquid chromatography-gas chromatography (LC-GC), and the system was applied to the extraction and analysis of polycyclic aromatic hydrocarbons (PAHs) in sediment. The method is of superior sensitivity compared with the traditional methods, and only a small 10 mg sample was required for analysis. The commercial extraction vessels were replaced by laboratory-made stainless steel vessels because of some problems that arose. The performance of the laboratory-made vessels was comparable to that of the commercial ones. In an investigation of the effect of thermal desorption in PHWE, it was found that at lower temperatures (200ºC and 250ºC) the effect of thermal desorption is smaller than the effect of the solvating property of hot water. At 300ºC, however, thermal desorption is the main mechanism. The effect of the geometry of the extraction vessel on recoveries was studied with five specially constructed extraction vessels. In addition to the extraction vessel geometry, the sediment packing style and the direction of water flow through the vessel were investigated. The geometry of the vessel was found to have only minor effect on the recoveries, and the same was true of the sediment packing style and the direction of water flow through the vessel. These are good results because these parameters do not have to be carefully optimised before the start of extractions. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) were compared as trapping techniques for PHWE. LLE was more robust than SPE and it provided better recoveries and repeatabilities than did SPE. Problems related to blocking of the Tenax trap and unrepeatable trapping of the analytes were encountered in SPE. Thus, although LLE is more labour intensive, it can be recommended over SPE. The stabilities of the PAHs in aqueous solutions were measured using a batch-type reaction vessel. Degradation was observed at 300ºC even with the shortest heating time. Ketones and quinones and other oxidation products were observed. Although the conditions of the stability studies differed considerably from the extraction conditions in PHWE, the results indicate that the risk of analyte degradation must be taken into account in PHWE. The aqueous solubilities of acenaphthene, anthracene and pyrene were measured, first below and then above the melting point of the analytes. Measurements below the melting point were made to check that the equipment was working, and the results were compared with those obtained earlier. Good agreement was found between the measured and literature values. A new saturation cell was constructed for the solubility measurements above the melting point of the analytes because the flow-through saturation cell could not be used above the melting point. An exponential relationship was found between the solubilities measured for pyrene and anthracene and temperature.

Solvent extraction of lanthanides and yttrium from nitrate medium with CYANEX 925 in heptane

The extraction behavior of lanthanides and yttrium usinsg CYANEX 925 (mixture of branched chain alkylated phosphine oxides) in n-heptane from nitrate medium has been studied. The effects of aqueous phase ionic strength, CYANEX 925 concentration in the organic phase, and temperature on Sm3+, Nd3+ and Y3+ extraction have been investigated. The extractability of the lanthanides and yttrium increases with increasing nitrate concentration, as well as with increasing CYANEX 925 concentration. An extraction mechanism is proposed based on slope analysis. Furthermore, the infra-red spectra of CYANEX 925 saturated with lanthanides are employed to provide evidence of the composition of the complex. The relationship between the logarithm of the distribution ratio and lanthanide atomic number is also discussed which indicates that yttrium can be separated from fight lanthanides. In addition separation of the light and heavy lanthanide groups is also possible using CYANEX 925. From the temperature dependence data, the thermodynamic parameters values (Delta H, Delta S and Delta G) are calculated.

Extraction and separation of cadmium(II), iron(III), zinc(II), and europium(III) by Cyanex302 solutions using hollow fiber membrane modules

The mass transfer behaviors of Cd(II), Fe(III), Zn(II), and Eu(III) in sulfuric acid solution using microporous hollow fiber membrane (HFM) containing bis(2,4,4-trimethylpentyl)monothiophosphinic acid (commercial name Cyanex302) were investigated in this paper. The experimental results showed that the values of the mass transfer coefficients (K-w) decreased with an increase of H+ concentration and increased with an increase of extractant Cyanex302 concentration. The mass transfer resistance of Eu3+ was the largest because K-w value of Eu3+ was the smallest. The order of mass transfer rate of metal ions at low pH was Cd > Zn > Fe > Eu. Mixtures of Zn2+ and Eu3+ or of Zn2+ and Cd2+ were well separated in a counter-current circulation experiment using two modules connected in series at different initial acidity and concentration ratio. These results indicate that a hollow fiber membrane extractor is capable of separating the mixture compounds by controlling the acidity of the aqueous solution and by exploiting different mass transfer kinetics. The interfacial activity of Cyanex302 in sulfuric acid solution was measured and interfacial parameters were obtained according to Gibbs adsorption equation.

Interfacial behavior of DEHEHP and the kinetics of cerium(IV) extraction in nitrate media

The effects of diluents, temperature, acidity, and ionic strength of the aqueous phase on the interfacial properties of DEHEHP have been extensively investigated using the Du Nouy ring method. In addition, the effect of cerium(IV) concentration loaded in the organic phase on the interfacial tension has also been studied. With the increase of DEHEHP concentration, the value of interfacial tension (gamma) decreases in the studied system, which shows that DEHEHP has interfacial activity as a kind of surfactant. The surface excess at the saturated interface (Gamma(max)) and the minimum bulk concentration of the extractant necessary to saturate the interface (C-min) under the different conditions are calculated according to two adsorption equations such as the Gibbs and Szyszkowski functions to be presented in comprehensive tables and figures. The relationship between the interfacial activity of DEHEHP and cerium(IV) extraction kinetics by DEHEHP has been discussed by considering different factors such as the effects of diluents and temperature. However, the interfacial activity parameter of extractant only is a qualitative parameter, but cannot provide strong enough evidence to quantitatively explain the relationship between extraction kinetics and interfacial properties of an extractant.

Synergistic extraction of rare earths by mixture of bis(2,4,4-trimethylpentyl)phosphinic acid and Sec-nonylphenoxy acetic acid

Synergistic extraction of trivalent rare earths (RE=Sc, Y, La, Gd, Yb) from hydrochloride medium using mixture of bis(2,4,4-trimethylpentyl)phosphinic acid (HL, Cyanex272) and Sec-nonylphenoxy acetic acid (HA, CA-100) in n-heptane has been studied. The synergistic enhancement coefficients were observed for La (1.30), Gd (1.97), Y (3.59), Yb (8.21) and Sc (14.41). The results indicated yttrium was extracted into n-heptane as YH(5)A(4)L(4) mixed species instead of Y(HL2)(3), Y(OH)(2)A(HA)(3) which were extracted by Cyanex272 and CA-100, respectively. A cation exchange mechanism was proposed and further clarified by IR spectra. The equilibrium constants, formation constants and thermodynamic functions such as Delta G, Delta H and Delta S were determined. The Cyanex272 + CA-100 system not only enhanced the extraction efficiency of RE but also improved the selectivities significantly. The mutual separation factors of these ions suggested the mixture system would be of practical value in extraction and separation of rare earths.